1. Field of the Invention
The present invention relates generally to an evaporative emission control system for automotive vehicles and, more particularly, to a method of testing an evaporative emission control system of an automotive vehicle.
2. Description of the Related Art
Automotive vehicles typically include a fuel tank and an evaporative emission control system that collects volatile fuel vapors generated in the fuel tank. The evaporative emission control system includes a vapor collection canister, usually containing an activated charcoal mixture, to collect and store the emitted fuel vapors. Normally, the vapor collection canister collects volatile fuel vapors which accumulate during refueling of the automotive vehicle or from increases in fuel temperature. During conditions conducive to purging the fuel vapors from the collection canister, a purge valve placed between an intake manifold and the canister is opened by an engine control unit in an amount determined by the engine control unit to purge the canister; i.e., the stored vapors are drawn into the intake manifold from the canister for ultimate combustion within a combustion chamber of an engine.
Governmental regulations require that certain vehicles powered by volatile fuels such as gasoline have their evaporative emission control systems checked to determine if a leak exists in the system. Therefore, there is a need in the art to provide on board vehicle diagnostic systems to determine if a leak is present in a portion of the evaporative emission control system.